In general, an air conditioner for vehicles is a car interior component, which is installed in the vehicle heat for the purpose of cooling the inside of the vehicle in the summer season or the winter season or removing frost from a windshield in rainy season or winter season to thereby secure a driver's front and rear visual field. Since such an air conditioner typically includes a heating device and a cooling device together, so that it heats, cools or ventilates the inside of the vehicle through the steps of selectively introducing the indoor air or the outdoor air to the air conditioner through a blower unit, heating or cooling the introduced air, and blowing the heated or cooled air into the vehicle.
Such an air conditioner is classified into a three-piece type where a blower unit, an evaporator unit, and a heater core unit are disposed independently, a semi-center type where the evaporator unit and the heater core unit are embedded in an air-conditioning case and the blower unit is mounted separately, and a center-mounting type where the three units are all embedded in the air-conditioning case.
FIG. 1 illustrates the semi-center type air conditioner. In FIG. 1, the air conditioner 1 includes: an air-conditioning case 10 having an air inflow port 11 formed on an inlet thereof and a defrost vent 12a, a face vent 12b and floor vents 12c and 12d mounted on an outlet thereof in such a way as to be controlled in their opened amount by mode doors 16; a blower (not shown) connected to the air inflow port 11 of the air-conditioning case 10 for sending indoor air or outdoor air; an evaporator 2 and a heater core 3 embedded in the air-conditioning case 10; and a temperature-adjusting door 15 mounted between the evaporator 2 and the heater core 3 for adjusting opened amounts of a cold air flow passageway P1 bypassing the heater core 3 and a warm air channel flow P2 passing through the heater core 3.
Furthermore, the floor vents 12c and 12d are divided into a floor vent 12c for a front seat and a floor vent 12d for a rear seat.
Moreover, the temperature-adjusting door 15 and a mode door 16 respectively include rotary shafts 15b and 16b rotatably mounted on both side walls of the air-conditioning case 10 and plates 15a and 16a formed at one side of the rotary shafts 15b and 16b. In this instance, as the mode door 16, a center pivot door having the plates 16a formed at both sides of the rotary shaft 16b may be used.
The temperature-adjusting door 15 and the mode door 16 are connected to a cam (not shown) or a lever (not shown), which is actuated by an actuator (not shown) mounted on an outer surface of the air-conditioning case 10, and rotatably operated to thereby adjust the opened amounts of the cold and warm air flow passageways P1 and P2 or adjust an opened amount of passageways facing toward the vents 12a to 12d. 
In addition, as shown in FIG. 2, the temperature-adjusting door 15 and the mode door 16 further include sealing members 15c and 16c attached to the edges of the plates 15a and 16a. The sealing members 15c and 16c are in close contact with a wall surface of the air-conditioning case 10 to improve sealability when the doors 15 and 16 close the corresponding passageways.
In the air conditioner 1 having the above structure, in case of the greatest cooling mode, the temperature-adjusting door 15 opens the cold air flow passageway P1 and closes the warm air flow passageway P2. Accordingly, the air blown by a blower (not shown) is converted into cold air by heat-exchanging with refrigerant flowing inside the evaporator 2 while passing through the evaporator 2, and then, flows toward a mixing chamber (MC) through the cold air flow passageway P1. After that, the converted air is discharged to the inside of a vehicle through the vents 12a to 12d opened according to a predetermined air-conditioning mode, whereby the inside of the vehicle is cooled.
Moreover, in case of the greatest heating mode, the temperature-adjusting door 15 closes the cold air flow passageway P1 and opens the warm air flow passageway P2. Accordingly, the air blown by a blower (not shown) passes through the evaporator 2, is converted into warm air by heat-exchanging with cooling water flowing inside the heater core 3 while passing through the heater core 3 through the warm air flow passageway P2, and then, flows toward the mixing chamber (MC). After that, the converted air is discharged to the inside of a vehicle through the vents 12a to 12d opened according to the predetermined air-conditioning mode, whereby the inside of the vehicle is heated.
In the meantime, in case of a half cooling mode, the temperature-adjusting door 15 is rotated to a neutral position, and opens the cold air flow passageway P1 and the warm air flow passageway P2 relative to the mixing chamber (MC). Accordingly, the cold air passing through the evaporator 2 and the warm air passing through the heater core 3 flow toward the mixing chamber (MC) and are mixed with each other, and then, are discharged to the inside of the vehicle through the vents 12a to 12d opened according to the predetermined air-conditioning mode.
The temperature-adjusting door 15 and the mode door 16 respectively have the sealing members 15c and 16c to increase sealability, but have a problem in that they generate a bad smell because of inhabitation of molds on the sealing members 15c and 16c. 
Furthermore, since the sealing members 15c and 16c mounted on the temperature-adjusting door 15 and the mode door 16 are is very expensive and require much time to mount them to the temperature-adjusting door 15 and the mode door 16, the manufacturing price is increased.
Moreover, since the plates 15a and 16a of the doors 15 and 16 have a predetermined thickness to allow mounting of the sealing member 15c and 16c, the doors 15 and 16 are very heavy and need great material costs by weight.